Question

In Asp.net. how can I access every checkbox exists in the page using C# code ?

Answer 1

This gets you every Checkbox on the page. You can change the form1 to whatever control you want to search inside of.

foreach (Control ctl in form1.Controls)
{
    if (ctl is CheckBox)
    {

    }
}

Alternatively if you know the ID of the control:

form1.FindControl("id");